1. Field of the Invention
The present invention relates to a display device with a built-in touch panel.
2. Description of the Related Art
Most touch panels currently in widespread use are of an external type that is used in combination with a display panel. Since the touch panel is a component that is separated from the display panel, it is difficult to reduce the entire thickness of the device. In contrast to this, in-cell touch panels, which are of a type that is incorporated into a display panel, have a structure contributing to a reduced thickness.
JP 2010-231186 A discloses that dummy electrodes are formed in a space between detection electrodes in an in-cell touch panel. This is effective, from the viewpoint of appearance, for equalizing reflectance to suppress the view of electrode. However, since the dummy electrode blocks an electric line of force from a counter electrode, it is preferable, in terms of the detection of a touch, that the dummy electrode is subdivided with many cuts formed therein.
In terms of appearance, a gap of all electrodes including detection electrodes and dummy electrodes is preferably 50 μm or less (particularly 30 μm or less), and the width of the detection electrode and the width of the dummy electrode are ideally equal to each other. By doing this, a uniform pattern distribution can be obtained, so that visibility can be most reduced. However, since the width and gap of the detection electrodes depend on the product specification, the dummy electrode cannot be necessarily subdivided in such dimensions. Actually, when the width of the dummy electrode is within ±15% with respect to the width of the detection electrode, an effect of reducing visibility can be sufficiently obtained.
Depending on the product specification, however, the gap of the dummy electrodes is reduced because of a narrow gap of the detection electrodes. Therefore, it is conceivable that detection sensitivity cannot be sufficiently assured. In this case, the dummy electrode has to be further subdivided. However, if doing so, a difference in density of pattern is generated between a detection electrode portion and a dummy electrode portion, visibility is increased, and thus the appearance is deteriorated. As a countermeasure, it is conceivable that the detection electrode is subdivided by dividing it into a plurality of portions to thereby be brought close to the subdivided pattern of the dummy electrode. However, this increases the resistance of the detection electrode in proportion to the number of divided portions, which is a new factor of reducing detection sensitivity.